The proposed research will deal with the structural basis underlying normal and altered function of the kidney. Experiments on acute renal failure will mainly deal with the relationship of cortical vasoconstriction to the recovery phase particularly to the onset of glomerular filtration. The ultrastructure of the thin limbs of Henle will be investigated with emphasis on comparative studies, analysis of the substructure of the intercellular junctions by the freeze-fracture technique, tracer experiments on junctional permeability and the study of the influence of anti-diuretic hormone on thin limb structure. Experiments on the renal vasculature will concentrate on the effect of polycations on glomerular permeability and structure, and the protein multiplier system in the renal medulla. Studies on the juxtaglomerular complex will focus on the structural basis for renin release following feedback stimulation of the renin secreting cells in vivo as well as in the isolated perfused kidney. Methods used are transmission, freeze-fracture and scanning electron microscopy, in vitro perfusion methods, tracer techniques including histochemistry, freeze substitution, morphometry and silicone rubber vascular casting.